The commercial ink cartridge for printer usually has a capacity of 400-600 ml. For spatial efficiency, the ink cartridge is mainly designed to shape as a long rectangular body, with the length/width ratio as high as 6 and more. A collapsible ink bag is disposed inside the cartridge to contain the ink for supplying ink when printing. Because of the amount of ink in the ink bag, the ink bag must be fixed inside the cartridge to prevent from the shaking or sliding of the ink bag inside cartridge during transportation. Hence, the surface of the ink bag is often partially glued to the inner wall of the cartridge. For replaceable ink cartridge, the entire cartridge is discarded when the ink is used up, which results in higher cost, waste of resource and additional pollution.
It is therefore desirable to devise a reusable ink bag to replace the known ink bag glued to the inside of the cartridge. Also, the structure of the cartridge must be redesigned to allow repeated opening and closing of the ink cartridge when replacing the ink bag. The conventional ink cartridge with large capacity is designed as a disposable product for one-time use. Thus, no reopening and reclosing of the cartridge is necessary after the lid and the cartridge body of the ink cartridge are closed. Therefore, the known cartridge usually has a structure of one-way engagement, i.e., once the lid and the cartridge body of the ink cartridge are engaged and closed, the brutal reopening of the cartridge is prone to damage some of the elements; otherwise, a specific auxiliary tool is required for reopening the cartridge, for example, by using screwdriver to disengage the lid and the cartridge body or inserting a tool into specific hole to press down a certain engagement part to disengage the lid and the cartridge body. All the above alternatives are inconvenient to the user.